A retrospective cohort study of leukemia and other cancers in benzene workers

Clinical encounter with three cancer patients affected by groundwater contamination at Camp Lejeune: a case series and review of the literature

Background

Advanced understanding of tumor biology has recently revealed the complexity of cancer genetics, intra/inter-tumor heterogeneity, and diverse mechanisms of resistance to cancer treatment. In turn, there has been a growing interest in cancer prevention and minimizing exposure to potential environmental carcinogens that surround us. In the 1980s, several chemical carcinogens, including perchloroethylene (PCE), trichloroethylene (TCE), and benzene, were detected in water systems supplying Camp Lejeune, a US Marine Corps Base Camp located in North Carolina.

Case presentation

This article presents three cases of cancer patients who have lived at Camp Lejeune, and, decades later, came to our clinic located 1000 miles from the original exposure site. The first patient is a young Caucasian man who was diagnosed with T cell acute lymphoblastic leukemia at the age of 37, and the second patient is a Caucasian man who had multiple types of cancer in the prostate, lung, and colon as well as chronic lymphocytic leukemia in his 60s and 70s. The third patient is another Caucasian man who had recurrent skin cancers of different histology, namely basal cell carcinomas, squamous cell carcinomas, and melanoma, from his 50s to 70s.

Conclusions

The US Congress passed the Honoring America’s Veterans and Caring for Camp Lejeune Families Act in 2012, which covers appropriate medical care for the people affected by the contamination. We hope that this article raises awareness about the history of Camp Lejeune’s water contamination among cancer care providers, so the affected patients can receive appropriate medical coverage and cancer screening across the country.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13256-022-03501-9.

Use of toxicant sensitivity distributions (TSD) for development of exposure guidelines for risk to human health from benzene

This technique for setting guideline values differs from that currently used by regulatory agencies throughout the world. Data for benzene were evaluated from epidemiological studies on human populations (29 studies). Exposure durations were evaluated in terms of Long Term Exposure (LTE) and Lifetime Exposure. All data was reported as Lowest Observed Adverse Effect Levels (LOAEL) and converted into exposure doses using Average Daily Dose (ADD) and Lifetime Average Daily Dose (LADD). These values were plotted as a Toxicant Sensitivity Distribution (TSD) which was the cumulative probability of LOAEL-ADD and LOAEL-LADD. From the TSD plots, linear regression equations gave correlation coefficients (R²) ranging from 0.69 to 0.97 indicating normal distributions. Guideline Values (GVs) for LTE (8hr/day) and Lifetime (24hr/70yrs) exposure to benzene were calculated using data from human epidemiological studies as 5% level of cumulative probability (CP) of LOAEL-ADD and LOAEL-LADD from the cumulative probability distributions (CPD). The derived guideline values from the human epidemiological studies were 92 μg/kg/day for LTE and 3.4 μg/kg/day for lifetime exposure. GV for LTE is appropriate for occupational exposure and GV derived for lifetime exposure appropriate for the general population. The guideline value for occupational exposure limit was below all the guideline values developed by regulatory agencies. But the general population guideline is within the range of values formulated by European Union, ATSDR, EPAQS, USEPA and OEHHA for air quality for the general population. This is an alternative method which eliminates the application of safety factors and other sources of errors in deriving guideline values for benzene.

BTEX exposure assessment and quantitative risk assessment among petroleum product distributors

The aim of this study was to evaluate benzene, toluene, ethylbenzene, and xylene (BTEX) exposure among workers at four stations of a major oil distribution company. Personal BTEX exposure samples were collected over working shift (8h) for 50 workers at four stations of a major oil distribution company in Iran. Measured mean values for workers across four sites were benzene (2437, 992, 584, and 2788μg/m³ respectively), toluene (4415, 2830, 1289, and 9407μg/m³), ethylbenzene (781, 522, 187, and 533μg/m³), and xylene (1134, 678, 322, and 525μg/m³). The maximum mean concentration measured across sites for benzene was 2788μg/m³ (Station 4), toluene was 9407μg/m³ (Station 4), ethylbenzene was 781μg/m³ (Station 1) and xylene was 1134μg/m³ (Station 1). The 8h averaged personal exposure benzene concentration exceeded the recommended value of 1600μg/m³ established by the Iranian Committee for Review and Collection of Occupational Exposure Limit and American Conference of Governmental Industrial Hygienists. Mean values for excess lifetime cancer risk for exposure to benzene were then calculated across workers at each site. Estimates of excess risk ranged from 1.74 ± 4.05 (Station 4) to 8.31 ± 25.81 (Station 3). Risk was assessed by calculation of hazard quotients and hazard indexes, which indicated that xylene and particularly benzene were the strongest contributors. Tanker loading was the highest risk occupation at these facilties. Risk management approaches to reducing exposures to BTEX compounds, especially benzene, will be important to the health of workers in Iran.

2-Phenethyl Isothiocyanate, Glutathione S-transferase M1 and T1 Polymorphisms, and Detoxification of Volatile Organic Carcinogens and Toxicants in Tobacco Smoke

Cigarette smoke contains relatively large quantities of volatile organic toxicants or carcinogens such as benzene, acrolein, and crotonaldehyde. Among their detoxification products are mercapturic acids formed from glutathione conjugation, catalyzed in part by glutathione S-transferases (GST). A randomized phase II clinical trial with a crossover design was conducted to evaluate the effect of 2-phenethyl isothiocyanate (PEITC), a natural product formed from gluconasturtiin in certain cruciferous vegetables, on the detoxification of benzene, acrolein, and crotonaldehyde in 82 cigarette smokers. Urinary mercapturic acids of benzene, acrolein, and crotonaldehyde at baseline and during treatment were quantified. Overall, oral PEITC supplementation increased the mercapturic acid formed from benzene by 24.6% (P = 0.002) and acrolein by 15.1% (P = 0.005), but had no effect on crotonaldehyde. A remarkably stronger effect was observed among subjects with the null genotype of both GSTM1 and GSTT1: in these individuals, PEITC increased the detoxification metabolite of benzene by 95.4% (P < 0.001), of acrolein by 32.7% (P = 0.034), and of crotonaldehyde by 29.8% (P = 0.006). In contrast, PEITC had no effect on these mercapturic acids in smokers possessing both genes. PEITC had no effect on the urinary oxidative stress biomarker 8-iso-prostaglandin F2α or the inflammation biomarker prostaglandin E2 metabolite. This trial demonstrates an important role of PEITC in detoxification of environmental carcinogens and toxicants which also occur in cigarette smoke. The selective effect of PEITC on detoxification in subjects lacking both GSTM1 and GSTT1 genes supports the epidemiologic findings of stronger protection by dietary isothiocyanates against the development of lung cancer in such individuals. Cancer Prev Res; 9(7); 598-606. ©2016 AACR.

Health risk characterization for exposure to benzene in service stations and petroleum refineries environments using human adverse response data

Health risk characterization of exposure to benzene in service stations and petroleum refineries has been carried out in previous studies using guideline values set by various agencies. In this work, health risk was characterized with the exposure data as cumulative probability distribution (CPD) plots but using human epidemiological data. This was achieved by using lowest observable adverse effects levels (LOAEL) data plotted as cumulative probability lowest effects distribution (CPLED). The health risk due to benzene was characterized by using probabilistic methods of hazard quotient (HQ50/50 and HQ95/5), Monte-Carlo simulation (MCS) and overall risk probability (ORP). CPD relationships of adverse health effects relationships and exposure data were in terms of average daily dose (ADD) and lifetime average daily dose (LADD) for benzene. For service station environments HQ50/50 and HQ95/5 were in a range of 0.000071-0.055 and 0.0049-21, respectively. On the other hand, the risk estimated for petroleum refinery environments suggests higher risk with HQ50/50 and HQ95/5 values ranging from 0.0012 to 77 and 0.17 to 560, respectively. The results of Monte-Carlo risk probability (MRP) and ORP indicated that workers in petroleum refineries (MRP of 2.9-56% and ORP of 4.6-52% of the affected population) were at a higher risk of adverse health effects from exposure to benzene as compared to exposure to benzene in service station environments (MRP of 0.051 -3.4% and ORP of 0.35-2.7% affected population). The adverse effect risk probabilities estimated by using the Monte-Carlo simulation technique and the ORP method were found to be generally consistent.

Global characteristics of childhood acute promyelocytic leukemia

Acute promyelocytic leukemia (APL) comprises approximately 5-10% of childhood acute myeloid leukemia (AML) cases in the US. While variation in this percentage among other populations was noted previously, global patterns of childhood APL have not been thoroughly characterized. In this comprehensive review of childhood APL, we examined its geographic pattern and the potential contribution of environmental factors to observed variation. In 142 studies (spanning >60 countries) identified, variation was apparent-de novo APL represented from 2% (Switzerland) to >50% (Nicaragua) of childhood AML in different geographic regions. Because a limited number of previous studies addressed specific environmental exposures that potentially underlie childhood APL development, we gathered 28 childhood cases of therapy-related APL, which exemplified associations between prior exposures to chemotherapeutic drugs/radiation and APL diagnosis. Future population-based studies examining childhood APL patterns and the potential association with specific environmental exposures and other risk factors are needed.

Urinary metabolites of a polycyclic aromatic hydrocarbon and volatile organic compounds in relation to lung cancer development in lifelong never smokers in the Shanghai Cohort Study

Exposures to polycyclic aromatic hydrocarbons (PAHs) from various environmental and occupational sources are considered a primary risk factor for lung cancer among lifelong never smokers, based largely on results from epidemiologic studies utilizing self-reported exposure information. Prospective, biomarker-based human studies on the role of PAH and other airborne carcinogens in the development of lung cancer among lifelong non-smokers have been lacking. We prospectively investigated levels of urinary metabolites of a PAH and volatile organic compounds in relation to lung cancer risk in a nested case-control study of 82 cases and 83 controls among lifelong never smokers of the Shanghai Cohort Study, a prospective cohort of 18 244 Chinese men aged 45-64 years at enrollment. We quantified three PAH metabolites: r-1,t-2,3,c-4-tetrahydroxy-1,2,3,4-tetrahydrophenanthrene (PheT), 3-hydroxyphenanthrene (3-OH-Phe) and total hydroxyphenanthrenes (total OH-Phe, the sum of 1-, 2-, 3- and 4-OH-Phe), as well as metabolites of the volatile organic compounds acrolein (3-hydroxypropyl mercapturic acid), benzene (S-phenyl mercapturic acid), crotonaldehyde (3-hydroxy-1-methylpropylmercapturic acid) and ethylene oxide (2-hydroxyethyl mercapturic acid). Urinary cotinine was also quantified to confirm non-smoking status. Compared with the lowest quartile, odds ratios (95% confidence intervals) for lung cancer risk for the highest quartile levels of PheT, 3-OH-Phe and total OH-Phe were 2.98 (1.13-7.87), 3.10 (1.12-7.75) and 2.59 (1.01-6.65) (all P trend < 0.05), respectively. None of the metabolites of the volatile organic compounds were associated with overall lung cancer risk. This study demonstrates a potentially important role of exposure to PAH in the development of lung cancer among lifelong never smokers.

A cohort study of intra-urban variations in volatile organic compounds and mortality, Toronto, Canada

This study investigated associations between long-term exposure to ambient volatile organic compounds (VOCs) and mortality. 58,760 Toronto residents (≥35 years of age) were selected from tax filings and followed from 1982 to 2004. Death information was extracted using record linkage to national mortality data. Land-use regression surfaces for benzene, n-hexane, and total hydrocarbons were generated from sampling campaigns in 2002 and 2004 and assigned to residential addresses in 1982. Cox regression was used to estimate relationships between each VOC and non-accidental, cardiovascular, and cancer mortality. Positive associations were observed for each VOC. In multi-pollutant models the benzene and total hydrocarbon signals were strongest for cancer. The hazard ratio for cancer that corresponded to an increase in the interquartile range of benzene (0.13 μg/m(3)) was 1.06 (95% CI = 1.02-1.11). Our findings suggest ambient concentrations of VOCs were associated with cancer mortality, and that these exposures did not confound our previously reported associations between NO2 and cardiovascular mortality.

Simultaneous determination of volatile organic compounds and carbonyls in mainstream cigarette smoke using a sorbent cartridge followed by two-step elution

We developed a simple method for the simultaneous determination of volatile organic compounds (VOCs) and carbonyls in the mainstream cigarette smoke using a sorbent cartridge at ambient temperature without the traditional cryogenic impinger. A sorbent cartridge is installed between intake filter and the pump of the smoking machine. Collection of cigarette mainstream smoke is performed according to the Canadian Intense regime or the ISO regime. As adsorbent, Carboxen 572 (CX-572) is the most suitable for collection of VOCs and carbonyls in the mainstream cigarette smoke. Elution of VOCs and carbonyls from CX-572 is performed by the two-step elution with carbon disulfide and methanol. VOCs are eluted by first elution with carbon disulfide and carbonyls are eluted by second elution with methanol. For VOCs, a portion of eluate is analyzed by gas chromatography-mass spectrometry. For carbonyls, a portion of eluate is derivatized with enriched 2,4-dinitrophenylhydrazine solution and analyzed by high-performance liquid chromatography. Measurement values by CX-572 cartridge method are very close to those obtained by traditional impinger method except for 2-butanone. Impinger methods use 2,4-dinitrophenylhydrazine solution containing 50% water and 2-butanone-DNPhydrazone may be hydrolyzed with water. In the CX-572 method, the hydrolysis of 2-butanone is prevented because the eluate solution contains no water. CX-572 method can measure cigarette smoke resulting from not only one whole cigarette but also from one puff volume because of its high sensitivity and simple operation.

Urinary levels of volatile organic carcinogen and toxicant biomarkers in relation to lung cancer development in smokers

Besides polycyclic aromatic hydrocarbons (PAH) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), which are established lung carcinogens, tobacco smoke also contains relatively large quantities of volatile organic carcinogens and toxicants, including 1,3-butadiene, ethylene oxide, benzene, acrolein and crotonaldehyde. Although animal experiments showed that some of these compounds can induce tumors in multiple organs including the lung, epidemiological studies of their relationship with lung cancer in smokers have not been reported. Therefore, in this study, we quantified urinary mercapturic acid metabolites of 1,3-butadiene, ethylene oxide, benzene, acrolein and crotonaldehyde in addition to urinary biomarkers for PAH, NNK and nicotine in 343 lung cancer cases and 392 matched controls among a cohort of 18,244 Chinese men in Shanghai, China, followed from 1986 to 2006. Compared with the lowest quartiles, highest quartiles of all measured mercapturic acids were associated with statistically significantly ~2-fold increased risk for lung cancer (all P's for trend <0.01) after adjustment for smoking intensity and duration. The positive associations between biomarkers of ethylene oxide, benzene or acrolein and lung cancer risk remained statistically significant after adjustment for biomarkers of PAH and NNK, whereas urinary total cotinine completely explained the mercapturic acid metabolites and lung cancer associations (all P's for trend ≥ 0.39). We conclude that mercapturic acid metabolites of 1,3-butadiene, ethylene oxide, benzene, acrolein and crotonaldehyde may not be independent risk predictors of lung cancer among Shanghai smokers, in contrast to biomarkers of PAH, NNK and nicotine exposure.

The acute pulmonary toxicity in mice induced by multiwall carbon nanotubes, benzene, and their combination

Carbon nanotubes (CNTs) have been synthesized and produced on large scale for their wide application. They have high absorption ability to organic contaminants (such as benzene) and can form CNTs-benzene combination with benzene. In this article, the acute pulmonary toxicity, induced by multiwall carbon nanotubes (MWCNTs), benzene, and their combination, was studied by administrating the three test materials into mice lungs via intratracheal instillation. The biochemical parameters in bronchoalveolar lavage fluid (BALF) and pathological lesions in lungs were used as endpoints to evaluate the pulmonary toxicity of the three test materials at 3-day and 7-day postexposure, respectively. After the mice were intratracheally instilled with MWCNTs, benzene and MWCNTs-benzene combination at doses of 6.67 mg/kg, 2.67 mg/kg, and 9.34 mg/kg (containing 6.67 mg/kg MWCNTs and 2.67 mg/kg benzene), the total protein, alkaline phosphatase (ALP), acid phosphatase (ACP), and lactate dehydrogenase (LDH) in BALF and pathological lesions in lungs were examined. At 3-day postexposure, MWCNTs induced obvious pulmonary toxicity and benzene only induced slight pulmonary toxicity, whereas their combination induced very severe pulmonary toxicity. At 7-day postexposure, MWCNTs and benzene did not induce pulmonary toxicity individually, whereas their combination still induced severe pulmonary toxicity. These data indicated that, at the instilled doses in this experiment, the MWCNTs can alone induce acute pulmonary toxicity in mice and the benzene does not induce pulmonary toxicity, but the pulmonary toxicity of MWCNTs is enhanced after they form MWCNTs-benzene combination with low dose of benzene. The enhanced pulmonary toxicity may be due to the change of MWCNTs aggregation ability after benzene is adsorbed on them.

Overview of benzene-induced aplastic anaemia

The scientific literature is replete with reports of cases of benzene-induced toxicity to the haematopoietic system. These mainly involve aplastic anaemia, the first cases of which were reported in 1897. At high level of benzene exposure (air concentration > 100 p.p.m.), the incidence of aplastic anaemia is approximately 1/100 individuals exposed, but this drops precipitously at lower levels of exposure (10-20 p.p.m.) to around 1/10,000. Factors that affect susceptibility may include high liver cytochrome P450 2E1 activity and low folic acid intake. The mechanism of benzene-induced aplastic anaemia remains unclear, but is likely to involve: (a) metabolism of benzene in the liver; (b) transport of metabolites to the marrow and their secondary activation to toxic quinones and free radicals by peroxidase enzymes; (c) induction of apoptosis, DNA damage and altered differentiation in early progenitor cells; and (d) depletion of the stem cell pool.

ATSDR evaluation of health effects of benzene and relevance to public health

As part of its mandate, the Agency for Toxic Substances and Disease Registry (ATSDR) prepares toxicological profiles on hazardous chemicals found at Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) National Priorities List (NPL) sites that have the greatest public health impact. These profiles comprehensively summarize toxicological and environmental information. This article constitutes the release of portions of the Toxicological Profile for Benzene. The primary purpose of this article is to provide public health officials, physicians, toxicologists, and other interested individuals and groups with an overall perspective on the toxicology of benzene. It contains descriptions and evaluations of toxicological studies and epidemiological investigations and provides conclusions, where possible, on the relevance of toxicity and toxicokinetic data to public health.

Genetic polymorphisms in hMTH1, hOGG1 and hMYH and risk of chronic benzene poisoning in a Chinese occupational population

Oxidative damage to DNA induced by benzene is an important mechanism of its genotoxicity, which leads to chronic benzene poisoning (CBP). Therefore, genetic variation in DNA repair genes may contribute to susceptibility to CBP in the exposed population. We hypothesized that single nucleotide polymorphisms (SNPs) in hMTH1, hOGG1 and hMYH genes are associated with risk of CBP. We genotyped SNPs at codon 83 of hMTH1, codon 326 of hOGG1, and codon 324 of hMYH in 152 CBP patients and 152 healthy workers occupationally exposed to benzene without poisoning manifestations. The genotypes were determined by polymerase chain reaction-restrained fragment length polymorphism (PCR-RFLP) technique. There were 2.51-fold [adjusted odds ratio (OR(adj)), 2.51; 95% CI, 1.14-5.49; P=0.02] and 2.49-fold (OR(adj), 2.49; 95% CI: 1.52-4.07; P<0.01) increased risk of CBP for individuals carrying genotypes of hMTH1 83Val/Met+Met/Met and hOGG1 326Cys/Cys, respectively. Compared with individuals carrying genotypes of hOGG1 326Cys/Cys and hMYH 324His/His at the same time, there was a 0.33-fold (OR(adj), 0.33; 95% CI: 0.15-0.72; P<0.05) decreased risk of CBP for those with genotypes of hOGG1 326Ser/Cys+Ser/Ser and hMYH 324His/Gln+Gln/Gln. In the smoking group, there was a 0.15-fold (OR(adj), 0.15; 95% CI, 0.03-0.68; P=0.01) decreased risk of CBP for subjects carrying genotypes of hMYH 324His/Gln+Gln/Gln compared with those of genotype of hMYH 324His/His. Therefore, our results suggested that polymorphisms at codons 83 of hMTH1 and codon 326 of hOGG1 might contribute to CBP in a Chinese occupational population.

Differentially expressed pro- and anti-apoptogenic genes in response to benzene exposure: Immunohistochemical localization of p53, Bag, Bad, Bax, Bcl-2, and Bcl-w in lung epithelia

Benzene, a well-known human carcinogen, is a commonly used industrial chemical that evokes further toxicological concern because of its potential genotoxic risks as a constituent of petrol and the byproduct of combustion and cigarette smoke. The present study investigated the effects of benzene inhalation on the expression of pro- and antiapoptogenic genes in lung epithelia. Immunohistochemical expression was assessed for antiapoptotic Bcl-2 family proteins, including Bcl-2, Bcl-w, and Bag-1 as well as proapoptotic subfamily members with Bcl-2 homology (BH)1 1-3, namely Bax, those that consist of only the BH3 region, represented by Bad, and proapoptotic gene expression for p53. Rats exposed to benzene via inhalation (300 ppm) for 7 days showed a significant upregulation of proapoptotic gene expression for p53, Bax, and Bad as assessed by a semiquantitative segmental analysis of the lung epithelia, including bronchioles, terminal bronchioles, respiratory bronchioles, and alveoli. Bag-1, an antiapoptogenic gene, was also found to have significant upregulated expression in lung epithelia. Since the underlying mechanisms by which Bag-1 exerts its antiapoptogenic effects are not known, benzene may target the protein chaperones hsc70/hsp70, or RING finger protein associated with Bag-1 activity. Alternatively, the significant downregulation of Bcl-2 may have diminished the antiapoptotic synergism necessary for the effectiveness of Bag-1. Both Bcl-2 and Bcl-w were found to be significantly downregulated compared to the proapoptotic counterparts. These data support the role of benzene in activating proapoptogenic events that lead to the upregulation of gene expression that may provide a crucial defense mechanism within lung parenchyma to reduce mutation hazard and potential carcinogenic effects of benzene-initiated pathogenesis.

Genetic polymorphisms and benzene metabolism in humans exposed to a wide range of air concentrations

Using generalized linear models with natural-spline smoothing functions, we detected effects of specific xenobiotic metabolizing genes and gene-environment interactions on levels of benzene metabolites in 250 benzene-exposed and 136 control workers in Tianjin, China (for all individuals, the median exposure was 0.512 p.p.m. and the 10th and 90th percentiles were 0.002 and 6.40 p.p.m., respectively). We investigated five urinary metabolites (E,E-muconic acid, S-phenylmercapturic acid, phenol, catechol, and hydroquinone) and nine polymorphisms in seven genes coding for key enzymes in benzene metabolism in humans {cytochrome P450 2E1 [CYP2E1, rs2031920], NAD(P)H: quinone oxidoreductase [NQO1, rs1800566 and rs4986998], microsomal epoxide hydrolase [EPHX1, rs1051740 and rs2234922], glutathione-S-transferases [GSTT1, GSTM1 and GSTP1(rs947894)] and myeloperoxidase [MPO, rs2333227]}. After adjusting for covariates, including sex, age, and smoking status, NQO1*2 (rs1800566) affected all five metabolites, CYP2E1 (rs2031920) affected most metabolites but not catechol, EPHX1 (rs1051740 or rs2234922) affected catechol and S-phenylmercapturic acid, and GSTT1 and GSTM1 affected S-phenylmercapturic acid. Significant interactions were also detected between benzene exposure and all four genes and between smoking status and NQO1*2 and EPHX1 (rs1051740). No significant effects were detected for GSTP1 or MPO. Results generally support prior associations between benzene hematotoxicity and specific gene mutations, confirm earlier evidence that GSTT1 affects production of S-phenylmercapturic acid, and provide additional evidence that genetic polymorphisms in NQO1*2, CYP2E1, and EPHX1 (rs1051740 or rs2234922) affect metabolism of benzene in the human liver.

Dangerous and cancer-causing properties of products and chemicals in the oil refining and petrochemical industries. Part XXX: Causal relationship between chronic myelogenous leukemia and benzene-containing solvents

Benzene and benzene-containing products and solvents have long been associated with bone marrow toxicity. Both animal studies and human epidemiological studies have shown statistically significant increases of leukemia and other lymphohematopoietic cancers in workers exposed to benzene. The most common leukemia that has been associated with benzene exposure, also called benzene poisoning, is acute myelocytic leukemia (AML). A review of the epidemiological literature on workers exposed to benzene or benzene-containing solvents and products shows, without question, that this exposure is significantly related to other types of leukemia and lymphoma. In this article, we review the literature on the relationship between benzene exposure and chronic myelogenous leukemia (CML) and find that benzene and benzene-containing products are significantly related to morbidity and mortality from CML.

The effects of benzene exposure on apoptosis in epithelial lung cells: localization by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) and the immunocytochemical localization of apoptosis-related gene products

Although benzene, a well-known human carcinogen, has been shown to induce apoptosis in vitro, no studies have been carried out to confirm and characterize its role in activating apoptosis in vivo. The present study investigated the effects of benzene inhalation on the epithelial cells lining the respiratory tract including bronchioles, terminal bronchioles, respiratory bronchioles and alveoli of male Sprague-Dawley rats. Inhalation of benzene 300 ppm for 7 days induced apoptotic changes in the parenchymal components in the lung that significantly exceeded the events of programmed cell death in normal control tissues. Apoptosis was confirmed by the electrophoretic analysis of internucleosomal DNA fragmentation of benzene-exposed lung tissues, which exhibited 180-200 bp laddering subunits indicative of genomic DNA degradation. Furthermore, semi-quantitative analysis of intracellular localization of terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling TUNEL) showed a significant (p < 0.001) increase in the apoptotic index calculated for bronchiolar 73.5%, terminal bronchiolar (65%), and respiratory bronchiolar 60.8% segmental epithelial components as well as alveolar (55%) epithelia. Analysis of immunohistochemical expression of apoptosis-related gene products also supported the hypothesis that benzene can induce apoptosis in chemosensitive target cells in the lung parenchyma. Quantitative immunhistochemistry showed a statistically significant increase p < 0.001 in the immunoreactive staining index for cytochrome c, Apaf-1 (apoptosis activating factor-1), DNA fragmentation factor, and representative cysteine proteases including caspase-1, caspase-2L, caspase-8 and caspase-9. Thus this is the first study of the respiratory system that demonstrates that benzene inhalation induces lung cell apoptosis as confirmed by DNA electrophoresis, in situ nick end labeling, and the upregulation of apoptosis-related gene products that facilitate caspase-cleaved enzymes which lead to cell degradation via programmed cell death. These responses may represent an important defense mechanism within the parenchymal cells of the respiratory system that reduce mutational hazard and the potential carcinogenic effects of benzene-initiated pathogenesis.

Carcinogenic effects of benzene: Cesare Maltoni's contributions

Cesare Maltoni's contributions to understanding, identifying, and characterizing widely used commercial chemicals in experimental animals are among the most important methods developed in the history of toxicology and serve to protect working men and women, the general population, and our environment from hazardous substances. Maltoni developed experimental methods that have reached the "platinum standard" for protection of public health. Benzene was among the 400 or more chemicals that Maltoni and his associates tested for carcinogenicity. In 1976, Maltoni reported that benzene is a potent experimental carcinogen. Maltoni's experiments clearly demonstrated that benzene is carcinogenic in Sprague-Dawley rats, Wistar rats, Swiss mice, and RF/J mice when administered by inhalation or ingestion. Benzene caused carcinomas of the Zymbal gland, oral cavity, nasal cavities; cancers of the skin, forestomach, mammary glands, and lungs; angiosarcomas and hepatomas of the liver; and hemolymphoreticular cancers. Thus, benzene was shown to be a multipotential carcinogen that produced cancers in several species of animals by various routes of administration. On November 2, 1977, Chemical Week reported that Maltoni provided a "bombshell" when he demonstrated the "first direct link" between benzene and cancer. In this paper, I shall summarize early experiments and human studies and reports; Maltoni's experimental contribution to understanding the carcinogenicity of benzene in humans and animals; earlier knowledge concerning benzene toxicity; and benzene standards and permissible exposure levels.

Myeloma aetiology and epidemiology

Recently there have been substantial improvements in our understanding of the biology of myeloma. These findings have important implications for aetiological studies aimed at defining the causative factors for myeloma. Myeloma is closely related to monoclonal gammopathy of unknown significance (MGUS), which is now recognized to be very common in the older population. The epidemiology of these conditions is presented and discussed in the context of the genetic factors governing both the risk of developing MGUS or of transformation to myeloma. Biological studies support a role for aberrant class switch recombination early in the natural history of myeloma suggesting that factors in the environment may interact with this mechanism to increase myeloma risk. Case-control and cohort studies have identified several known and suspected environmental exposures. These exposures include high doses of ionizing radiation, and occupational exposure in the farming and petrochemical industries. The data supporting these associations are presented and discussed in the context of the molecular mechanisms underlying these exposures. In particular DNA damage occurring as a consequence could readily interact with the class switch recombination process to increase the risk of chromosomal translocations, oncogene deregulation and malignant transformation. A further hypothesis, which has been extensively investigated, is the role of chronic immune/antigenic stimulation and the risk of myeloma. This concept is difficult to explain in the context of our current immunological concepts. The data supporting the association and how molecular epidemiological studies using genetic variants in cytokine genes are allowing us to revisit this concept are discussed in detail.

Dietary factors and stomach cancer mortality

The present study examined the relationship between stomach cancer and the low intake of fresh fruit and vegetables and/or a high intake of pickled, preserved or salted foods and frequent use of cooking oil. During 139,390 person-year of follow-up of over 13,000 subjects, 116 died from stomach cancer. Using a Cox proportional hazards-regression analysis of relative risk (RR, 95% CI) controlling for age, sex, smoking and other dietary factors, a significant decline was found with a high consumption of green and yellow vegetables (RR=0.4, 95% CI=0.2-0.9). Reductions of between 40 and 50% were also observed with a high consumption of fresh foods (fruit, cuttle fish, tofu, and potatoes), but these associations were not statistically significant. The risk was significantly increased by the high consumption of processed meat (RR=2.7, 95% CI=1.0-7.4) and by the frequent use of cooking oil (RR=4.0, 95% CI=1.3-11.8). The high consumption of pickled food and traditional soups also increased risk, but not significantly. The findings suggest that a diet high in salt and low in vitamins may be associated with an increase in stomach cancer.

Benzene and lymphohematopoietic malignancies in humans

BACKGROUND

Quantitative evaluations of benzene-associated risk for cancer have relied primarily on findings from a cohort study of highly exposed U.S. rubber workers. An epidemiologic investigation in China (NCI/CAPM study) extended quantitative evaluations of cancer risk to a broader range of benzene exposures, particularly at lower levels.

METHODS

We review the evidence implicating benzene in the etiology of hematopoietic disorders, clarify methodologic aspects of the NCI/CAPM study, and examine the study in the context of the broader literature on health effects associated with occupational benzene exposure.

RESULTS

Quantitative relationships for cancer risk from China and the U.S. show a relatively smooth increase in risk for acute myeloid leukemia and related conditions over a broad dose range of benzene exposure (below 200 ppm-years mostly from the China study and above 200 ppm-years mostly from the U.S. study).

CONCLUSIONS

Risks of acute myeloid leukemia and other malignant and nonmalignant hematopoietic disorders associated with benzene exposure in China are consistent with other information about benzene exposure, hematotoxicity, and cancer risk, extending evidence for hematopoietic cancer risks to levels substantially lower than had previously been established. Published 2001 Wiley-Liss, Inc.

Benzene in the environment: an assessment of the potential risks to the health of the population

OBJECTIVES

Benzene has long been recognised as a carcinogen and recent concern has centred on the effects of continuous exposure to low concentrations of benzene both occupationally and environmentally. This paper presents an overview of the current knowledge about human exposure to benzene in the United Kingdom population based on recently published data, summarises the known human health effects, and uses this information to provide a risk evaluation for sections of the general United Kingdom population.

METHOD

Given the minor contribution that non-inhalation sources make to the overall daily intake of benzene to humans, only exposure from inhalation has been considered when estimating the daily exposure of the general population to benzene. Exposure of adults, children, and infants to benzene has been estimated for different exposure scenarios with time-activity patterns and inhalation and absorption rates in conjunction with measured benzene concentrations for a range of relevant microenvironments. Exposures during refuelling and driving, as well as the contribution of active and passive tobacco smoke, have been considered as part of the characterisation of risk of the general population.

RESULTS

Infants (<1 years old), the average child (11 years old), and non-occupationally exposed adults, receive average daily doses in the range of 15-26, 29-50, and 75-522 microg of benzene, respectively, which correspond to average ranges to benzene in air of 3.40-5.76 microg/m(3), 3.37-5.67 microg/m(3), and 3.7-41 microg/m(3) for infants, children, and adults, respectively. Infants and children exposed to environmental tobacco smoke have concentrations of exposure to benzene comparable with those of an adult passive smoker. This is a significant source of exposure as a 1995 United Kingdom survey has shown that 47% of children aged 2-15 years live in households where at least one person smokes. The consequence of exposure to benzene in infants is more significant than for children or adults owing to their lower body weight, resulting in a higher daily intake for infants compared with children or non-smoking adults. A worst case scenario for exposure to benzene in the general population is that of an urban smoker who works adjacent to a busy road for 8 hours/day-for example, a maintenance worker-who can receive a mean daily exposure of about 820 microg (equal to an estimated exposure of 41 microg/m(3)). The major health risk associated with low concentrations of exposure to benzene has been shown to be leukaemia, in particular acute non-lymphocytic leukaemia. The lowest concentration of exposure at which an increased incidence of acute non-lymphocytic leukaemia among occupationally exposed workers has been reliably detected, has been estimated to be in the range of 32-80 mg/m(3). Although some studies have suggested that effects may occur at lower concentrations, clear estimates of risk have not been determined, partly because of the inadequacy of exposure data and the few cases.

CONCLUSIONS

Overall the evidence from human studies suggests that any risk of leukaemia at concentrations of exposure in the general population of 3.7-42 microg/m(3)-that is at concentrations three orders of magnitude less than the occupational lowest observed effect level-is likely to be exceedingly small and probably not detectable with current methods. This is also likely to be true for infants and children who may be exposed continuously to concentrations of 3.4-5.7 microg/m(3). As yet there is no evidence to suggest that continuous exposures to these environmental concentrations of benzene manifest as any other adverse health effect.

Non-Hodgkin's lymphoma and exposure to benzene in a multinational cohort of more than 308,000 petroleum workers, 1937 to 1996

Petroleum workers are exposed to benzene or benzene-containing petroleum products. As such, studies of these workers provide an opportunity for investigating the relationship between benzene and non-Hodgkin's lymphoma (NHL). However, few cohort studies of petroleum workers report results of NHL separately. One reason is that NHL is usually grouped with other lymphopoietic cancers in the analysis. Another reason is the relatively small number of NHL cases in some studies. To determine the risk of NHL in petroleum workers, we identified 26 cohorts of petroleum workers in the United States, the United Kingdom, Canada, Australia, Italy, and Finland. Authors of the original studies were contacted, and data on the number of observed deaths and person-years of observation were requested. Data from these studies were reviewed individually as well as combined in a pooled analysis (meta-analysis). In particular, results for individual cohorts, most of which had never been reported before, were presented. The combined multinational cohort consisted of more than 308,000 petroleum workers (6.6 million person-years), and the observation period covered an interval of 60 years from 1937 to 1996. A total of 506 NHL deaths were observed, compared with 561.68 expected. The standardized mortality ratio was 0.90 and the 95% confidence interval was 0.82 to 0.98. Analyses were performed by type of facility and industrial process. Stratum-specific standardized mortality ratios (95% confidence intervals) were 0.96 (0.86 to 1.07) for US refinery workers, 1.12 (0.90 to 1.37) for non-US refinery workers, 0.64 (0.50 to 0.82) for product (gasoline) distribution workers, and 0.68 (0.47 to 0.95) for crude oil workers. When individual cohorts were stratified by length of observation, no pattern was detected. In general, exposure levels before 1950 were much higher than thereafter. However, analysis of workers by hire date (< 1950, > or = 1950) revealed no difference in NHL mortality. Furthermore, none of the individual studies showed significant exposure-response relations. In summary, results from individual studies, as well as from the pooled analysis, indicated that petroleum workers were not at an increased risk of NHL as a result of their exposure to benzene or other benzene-containing petroleum products in their work environment. This conclusion was supported by cohort studies of workers in other industries who were exposed to benzene as well as by population-based case-control studies of NHL and occupational exposures.

The contribution of benzene to smoking-induced leukemia

Cigarette smoking is associated with an increased risk of leukemia; benzene, an established leukemogen, is present in cigarette smoke. By combining epidemiologic data on the health effects of smoking with risk assessment techniques for low-dose extrapolation, we assessed the proportion of smoking-induced total leukemia and acute myeloid leukemia (AML) attributable to the benzene in cigarette smoke. We fit both linear and quadratic models to data from two benzene-exposed occupational cohorts to estimate the leukemogenic potency of benzene. Using multiple-decrement life tables, we calculated lifetime risks of total leukemia and AML deaths for never, light, and heavy smokers. We repeated these calculations, removing the effect of benzene in cigarettes based on the estimated potencies. From these life tables we determined smoking-attributable risks and benzene-attributable risks. The ratio of the latter to the former constitutes the proportion of smoking-induced cases attributable to benzene. Based on linear potency models, the benzene in cigarette smoke contributed from 8 to 48% of smoking-induced total leukemia deaths [95% upper confidence limit (UCL), 20-66%], and from 12 to 58% of smoking-induced AML deaths (95% UCL, 19-121%). The inclusion of a quadratic term yielded results that were comparable; however, potency models with only quadratic terms resulted in much lower attributable fractions--all < 1%. Thus, benzene is estimated to be responsible for approximately one-tenth to one-half of smoking-induced total leukemia mortality and up to three-fifths of smoking-related AML mortality. In contrast to theoretical arguments that linear models substantially overestimate low-dose risk, linear extrapolations from empirical data over a dose range of 10- to 100-fold resulted in plausible predictions.

China's "market economics in command": footwear workers' health in jeopardy

This study of occupational safety and health (OSH) problems in the footwear industry in China, the world's largest shoemaker, is based on four years of research in China supplemented by research in Taiwan, Australia, and the United States. With the advent of the economic reforms of the early 1980s, the Chinese state is being driven by an economic imperative under which the profit motive overrides other concerns, causing a deterioration in OSH conditions. Footwear workers are being exposed to high levels of benzene, toluene, and other toxic solvents contained in the adhesives used in the shoe-making process. Many workers have been afflicted with aplastic anemia, leukemia, and other health problems. Most of China's current permissible exposure limits to toxins are either outdated or underenforced. As a result, the Chinese state's protection of footwear workers' health is inadequate. The article aims to draw the attention of the international OSH community to the importance of setting specific exposure standards for the footwear industry worldwide.

A critique of the exposure assessment in the epidemiologic study of benzene-exposed workers in China conducted by the Chinese Academy of Preventive Medicine and the US National Cancer Institute

As reviewed in some detail in the present paper, workers employed in a wide variety of industries were included in the Chinese benzene study, and were exposed to not only benzene but also a wide range of other industrial chemicals. To attribute any or all health effects observed in the exposed cohort to benzene without examining other concomitant exposures is not appropriate. Although it was stated that one of the major objectives of the expanded study was to examine the effects of other risk factors, no such examination was made in any of the analyses in the expanded CAPM-NCI study. The CAPM-NCI study suffered from a number of limitations. One of the most serious limitations of the study involved the exposure estimates developed by the US NCI team. Comparing the assumptions used in the development of estimates and the exposure estimates themselves to actual data reported previously by the Chinese investigators revealed numerous inconsistencies and, in many cases, large discrepancies. It appeared that the exposure estimates were consistently lower than the actual exposure data. The so-called indirect validation conducted by the NCI team served no useful purpose, since by definition it could not validate the absolute values of the estimates. NCI was fully aware of some of the inadequacies of its exposure estimates. Although in a 1994 paper, the NCI team recognized that little confidence could be attached to the estimated (e.g., only 2% of the estimates for the time interval 1949-1959 and only 6% of the estimates prior to 1975 were rated in the high confidence category), the inadequacy of the estimates was never mentioned or discussed in any subsequent analyses or in the latest report (Hayes et al., 1998). Instead, the exposure of the workers was hailed as "well characterized" (Hayes et al., 1998). In conclusion both CAPM and NCI have made substantial efforts in studying the relationship between benzene exposure and various malignancies. Unfortunately, there were many inherent problems in the data as well as serious limitations in the exposure estimates. Because of these unresolved problems and limitations, many of the results in the CAPM-NCI study are unreliable. Therefore, the conclusions of the study, particularly those involving exposure estimates, are not justified.

An evaluation of modeled benzene exposure and dose estimates published in the Chinese-National Cancer Institute collaborative epidemiology studies

Risk estimates and cause and effect determinations are directly dependent on exposure and dose-response relationships. Recently, relative risks and excess cancer mortality attributed to occupational benzene exposure have been published in collaborative studies conducted by Chinese investigators and scientists from the National Cancer Institute. The results of these studies suggest increased risk of acute nonlymphocytic leukemia at relatively low benzene concentrations and associations with cancers not previously associated with benzene exposure. These studies are potentially important due to their size and potential to more thoroughly investigate the link between benzene exposure and cancer. However, there are questions concerning the validity of exposure and dose estimates supporting relative risk characterizations in these studies. Apparent discrepancies between modeled exposure and dose estimates and sources of actual measured exposure information and clinical markers of benzene toxicity raise serious concerns questioning the reliability of relative risk and cancer associations stated in these studies.

Hydroquinone, a reactive metabolite of benzene, inhibits NF-kappa B in primary human CD4+ T lymphocytes

Hydroquinone (HQ), a reactive metabolite of benzene, is present in cigarette smoke and is known to inhibit mitogen-stimulated activation of both T and B lymphocytes. Despite extensive study, the underlying mechanism for HQ's immunotoxicity is not clear. NF-kappa B is a transcription factor known to regulate the expression of a number of genes critical for normal T cell activation. We therefore hypothesized that NF-kappa B might be involved in HQ-induced immunosuppression. In this study, we demonstrate that 1 microM HQ inhibits tumor necrosis factor alpha induced activation of NF-kappa B in primary human CD4+ T cells. This inhibition is not accompanied by a loss in viability, and HQ-treated T cells maintain other active signaling pathways throughout the exposure duration. Additionally, the inhibition of NF-kappa B is reversible as HQ-treated T cells regain normal functioning after 72 h in culture. HQ does not appear to alter NF-kappa B directly as preincubation of nuclear extracts with HQ does not diminish activity of this protein. We further demonstrate that 1 microM HQ inhibits intracellular IL-2 production in T cells stimulated with phorbol ester but does not alter surface expression of CD25 (the alpha-subunit of the IL-2 receptor). These data suggest that NF-kappa B may be an important molecular mediator of HQ's (and benzene's) immunotoxicity.

Benzene--a review of the literature from a health effects perspective

A literature review of the impact on human health of exposure to benzene was conducted. Special emphasis in this report is given to the health effects reported in excess of national norms by participants in the Benzene Subregistry of the National Exposure Registry--people having documented exposure to benzene through the use of benzene-contaminated water for domestic purposes. The health effects reported in excess (p < or = .01) by some or all of the sex and age groups studied were diabetes, kidney disease, respiratory allergies, skin rashes, and urinary tract disorders; anemia was also increased for females, but not significantly so.

Benzene-, catechol-, hydroquinone- and phenol-induced cell transformation, gene mutations, chromosome aberrations, aneuploidy, sister chromatid exchanges and unscheduled DNA synthesis in Syrian hamster embryo cells

Benzene is a human carcinogen present naturally in petroleum and gasoline. For the simultaneous assessment of benzene-induced carcinogenicity and mutagenicity, benzene and its principal metabolites, phenol, catechol and hydroquinone were examined for their ability to induce cell transformation and genotoxic effects using the same mammalian cells in culture. Each of the four compounds induced morphological transformation of Syrian hamster embryo (SHE) cells. Catechol was the most potent, inducing transformation at concentrations of 1-30 microM, followed by hydroquinone (3-30 microM), phenol (10-100 microM) and benzene (only at 100 microM). Gene mutations at two loci in SHE cells were induced by all four compounds, with catechol being the most potent; both ouabain-resistant and 6-thioguanine-resistant mutant frequencies were increased. Chromosomal aberrations in SHE cells were especially induced by catechol, lesser by hydroquinone, and to a marginal extent by phenol at only the 100 microM concentration, whereas sister chromatid exchanges in SHE cells occurred with hydroquinone (1-30 microM), catechol (10-30 microM) and phenol (1000-3000 microM). Aneuploidy in the near diploid range of SHE cells was significantly induced by benzene and catechol. All three metabolites induced unscheduled DNA synthesis in SHE cells, whereas benzene did not. This is the first report that the cell transforming activity and mutagenicity of benzene and its metabolites were assessed with the same mammalian cells in culture. The results provide evidence that benzene and several of its metabolites are cell transforming and genotoxic to cultured mammalian cells.

Mortality among benzene-exposed workers in China

A large cohort of 74,828 benzene-exposed and 35,805 nonexposed workers employed between 1972 and 1987 in 12 cities in China was followed to determine mortality from all causes. Benzene-exposed study subjects were employed in a variety of occupations including coating applications, and rubber, chemical, and shoe production. Mortality was slightly increased among workers with greater cumulative exposure to benzene (ptrend < 0.05), but this excess was largely due to cancer deaths (ptrend < 0.01). Deaths due to lymphatic and hematopoietic malignancies (ptrend = 0.01) and lung cancer (ptrend = 0.01) increased with increasing cumulative exposure to benzene. Investigations continue to relate benzene exposure to specific lymphatic and hematopoietic malignancies and other causes of death.

An expanded cohort study of cancer among benzene-exposed workers in China. Benzene Study Group

An expanded cohort study of 74,828 benzene-exposed and 35,805 unexposed workers were followed during 1972 to 1987, based on a previous study in 12 cities in China. A small increase was observed in total cancer mortality among benzene-exposed compared with unexposed workers (relative risk [RR] = 1.2). Statistically significant excesses were noted for leukemia (RR = 2.3), malignant lymphoma (RR = 4.5), and lung cancer (RR = 1.4). When risks were evaluated by leukemia subtype, only acute myelogenous leukemia was significantly elevated (RR = 3.1), although nonsignificant excesses were also noted for chronic myelogenous leukemia (RR = 2.6) and acute lymphocytic leukemia (RR = 2.3). A significant excess was also found for aplastic anemia.

Clinical features of hematopoietic malignancies and related disorders among benzene-exposed workers in China. Benzene Study Group

Previous occupational cohort studies of benzene-exposed workers have for the most part used only death certificates to validate diagnoses of workers developing leukemia and other hematopoietic and lymphoproliferative malignancies and related disorders (HLD). In a follow-up study of 74,828 benzene-exposed workers and a comparison group of 35,805 nonexposed workers from 12 cities in China, we sought to characterized clinicopathologically and to confirm diagnoses of all cases of HLD. Using medical records, laboratory hematology results, and histopathology, U.S. and Chinese expert hematopathologists, blinded to exposure status, carried out a detailed review using standardized evaluation forms. Key among the findings were a notable diversity of malignant and nonneoplastic hematopoietic and lymphoproliferative disorders, documentation of excess myelodysplastic syndromes among benzene workers, and widespread dyspoiesis involving all hematopoietic cell lines. As sophisticated clinicopathologic characterization and corresponding classification schemes for HLD become increasingly widespread, it is recommended that future epidemiologic investigations of benzene workers incorporate similarly detailed morphologic evaluation. In extending follow-up of this cohort of young workers, we will continue to use all available clinical, laboratory hematology, and pathology data as well as cytogenetic and biochemical markers to characterized various HLD outcomes. These careful surveillance mechanisms should also provide additional insight into carcinogenic mechanisms of benzene and allow comparison of the molecular pathogenesis of HLD induced by benzene versus chemotherapy, radiation, or other exposure.

Haematopoietic cancer mortality among vehicle mechanics

OBJECTIVE AND METHODS

This historical cohort study investigated causes of death among car and mobile equipment mechanics in the District of Columbia's Department of Public Works. Men who were employed for at least one year between 1977 and 1989 were eligible for inclusion in the cohort; follow up was up to the end of 1991. Three cases of leukaemia (index cases) had been reported among these workers before the inception of this study. This research was undertaken to estimate the relative risk of haematological cancer among mechanics working for the District of Columbia.

RESULTS

Among the 335 male fleet maintenance workers, the all cause standardised mortality ratio (SMR) was 0.50 (33 observed deaths, 95% confidence interval (95% CI) 0.35-0.70), and the all cancer SMR was 0.55 (nine deaths, 95% CI 0.25-1.05). Three deaths from lymphatic and haematopoietic cancer were observed; the SMR was 3.63 (95% CI 0.75-10.63). In the subgroup with highest potential for exposure to fuels and solvents, the SMR for leukaemia and aleukaemia was 9.26 (two deaths, 95% CI 1.12-33.43), and the SMR for other lymphatic and haematopoietic neoplasms was 2.57 (one death from malignant lymphoma, 95% CI 0.06-14.27). All three lymphatic and haematopoietic cancer deaths were among car and mobile equipment mechanics (one was an index case). The two additional index cases were a fourth mechanic who died of leukaemia in 1992, after mortality follow up ended, and a fifth mechanic who was diagnosed with leukaemia in 1988 and is still alive.

CONCLUSION

Many garage mechanics in this cohort regularly used petrol to clean parts and to wash their hands; some workers would occasionally siphon petrol by mouth. Benzene, a recognised cause of haematological cancer, is a component of petrol. Previous research indicates that garage mechanics may be at risk of leukaemia and other haematological cancers, presumably due to exposure to petrol; this study supports those findings.

Benzene induces gene-duplicating but not gene-inactivating mutations at the glycophorin A locus in exposed humans

Occupational exposure to benzene is known to cause leukemia, but the mechanism remains unclear. Unlike most other carcinogens, benzene and its metabolites are weakly or nonmutagenic in most simple gene mutation assays. Benzene and its metabolites do, however, produce chromosomal damage in a variety of systems. Here, we have used the glycophorin A (GPA) gene loss mutation assay to evaluate the nature of DNA damage produced by benzene in 24 workers heavily exposed to benzene and 23 matched control individuals in Shanghai, China. The GPA assay identifies stem cell or precursor erythroid cell mutations expressed in peripheral erythrocytes of MN-heterozygous subjects, distinguishing the NN and N phi mutant variants. A significant increase in the NN GPA variant cell frequency (Vf) was found in benzene-exposed workers as compared with unexposed control individuals (mean +/- SEM, 13.9 +/- 1.7 per million cells vs. 7.4 +/- 1.1 per million cells in control individuals; P = 0.0002). In contrast, no significant difference existed between the two groups for the N phi Vf (9.1 +/- 0.9 vs. 8.8 +/- 1.8 per million cells; P = 0.21). Further, lifetime cumulative occupational exposure to benzene was associated with the NN Vf (P = 0.005) but not with the N phi Vf (P = 0.31), suggesting that NN mutations occur in longer-lived bone marrow stem cells. NN variants result from loss of the GPA M allele and duplication of the N allele, presumably through recombination mechanisms, whereas NO variants arise from gene inactivation, presumably due to point mutations and deletions. Thus, these results suggest that benzene produces gene-duplicating mutations but does not produce gene-inactivating mutations at the GPA locus in bone marrow cells of humans exposed to high benzene levels. This finding is consistent with data on the genetic toxicology of benzene and its metabolites and adds further weight to the hypothesis that chromosome damage and mitotic recombination are important in benzene-induced leukemia.

Cancer incidence and mortality near the Baglan Bay petrochemical works, South Wales

OBJECTIVES

To study incidence and mortality of leukaemias, cancer of the larynx, and other cancers near the petrochemical plant at Baglan Bay, in response to local concerns of an alleged cluster of cancers in the vicinity.

METHODS

This is a small area study of cancer incidence, 1974-84 and of mortality, 1981-91 based on the national postcoded data held by the Small Area Health Statistics Unit and with population and socioeconomic data from the 1981 census. The study is centred on BP Chemicals Ltd, Baglan Bay, Port Talbot, West Glamorgan, South Wales and includes a general population sample of 115,721 people (1981 census) living within 7.5 km of the plant. Cancer incidence and mortality for all cancers, leukaemias, and cancer of the larynx were examined within 7.5 km and 3 km of the plant, and tests for decline in risk of these cancers with distance from the plant were carried out. Mortality from several other cancers possibly associated with the petrochemical industry was also studied.

RESULTS

There were 5417 incident cancer cases and 2458 cancer deaths within 7.5 km of the plant during the periods of study. There was an 8% excess incidence of all cancers within 7.5 km, and a 24% excess of cancer of the larynx, consistent with a general excess of these cancers in West Glamorgan, but no apparent decline in incidence with distance from the plant, nor excess mortality. There was also no evidence of decline in leukaemia incidence or mortality with distance, at all ages or in children. Among the other causes included in the mortality study, there was an excess of multiple myeloma within 7.5 km, especially among women, and a significant decline in mortality from non-Hodgkin's lymphomas although there was no excess overall within 7.5 km.

CONCLUSIONS

The apparent excess incidence of all cancers and cancer of the larynx within 7.5 km of the BP Chemical Ltd works was consistent with an excess more generally in West Glamorgan, possibly related, at least to some extent, to cancer registration in Wales. There was no excess mortality from these cancers. The results for multiple myeloma and especially non-Hodgkin's lymphomas may have been chance findings in view of the multiple tests of significance carried out in the study. A study of lymphatic and haematopoietic cancers near oil refineries in Great Britain is to be undertaken that will help put the findings of the present study in wider context.

Incidence of leukaemia and lymphoma in young people in the vicinity of the petrochemical plant at Baglan Bay, South Wales, 1974 to 1991

OBJECTIVE

To determine whether there was an increased incidence of leukaemias and lymphomas in young people aged less than 25 years in the locality of a petrochemical plant at Baglan Bay, South Wales.

METHODS

Geographical population based study to compare the observed and expected incidence of leukaemia and lymphoma with onset before the age of 25, in the years 1974 to 1991. The population was aged 0-24 years and lived within 1.5 and 3 km of the plant. The observed number of cases in various categories were compared with the expected numbers of cases calculated from the Welsh cancer registration rates.

RESULTS

Although the observed numbers were generally greater than would be expected, none of the comparisons showed significant excess of leukaemias or lymphomas for any period of years.

CONCLUSIONS

The study shows that the incidence of leukaemias and lymphomas in children and young people in the area around the BP Chemical site at Baglan Bay, South Wales, between the years 1974 and 1991 was not significantly greater than normal.

Enhanced anaerobic degradation of benzene by enrichment of mixed microbial culture and optimization of the culture medium

A heterogeneous mixed culture, originally collected from two different sources, namely cow-drug and sludge from the city waste-water treatment plant, was grown in mineral medium containing 1% glucose and then adapted on benzene as the carbon and energy source. Under anaerobic conditions benzene was degraded via benzoic acid as a major intermediate in the benzene degradation pathway. The degradation rate of benzene was improved stepwise by the number of enrichments and optimization of the culture medium. The effects of microaerobic conditions and/or physicochemical treatment with H2O2 prior to anaerobic degradation were studied with respect to variations in benzene degradation rate, growth of biomass and gas composition. It was noticed that the amount of gas produced is less than the theoretical value expected and the percentage of methane in the product gas was very small (3%-3.5%). The reason for this is not well understood but it is presumed that the major group of benzene-degrading bacteria present in the culture medium are sulphate reducers and the mixed consortium is unable to degrade certain complex aromatic intermediates in the benzene degradation pathway under the experimental conditions. For an actual explanation of the situation arising in this study, further investigations must be carried out. However, the mixed culture is capable of oxidizing benzene more rapidly to intermediate compounds and also partly into gas under the culture conditions, compared to the published data for the anaerobic degradation of benzene.

On cancer risk estimation of urban air pollution

The usefulness of data from various sources for a cancer risk estimation of urban air pollution is discussed. Considering the irreversibility of initiations, a multiplicative model is preferred for solid tumors. As has been concluded for exposure to ionizing radiation, the multiplicative model, in comparison with the additive model, predicts a relatively larger number of cases at high ages, with enhanced underestimation of risks by short follow-up times in disease-epidemiological studies. For related reasons, the extrapolation of risk from animal tests on the basis of daily absorbed dose per kilogram body weight or per square meter surface area without considering differences in life span may lead to an underestimation, and agreements with epidemiologically determined values may be fortuitous. Considering these possibilities, the most likely lifetime risks of cancer death at the average exposure levels in Sweden were estimated for certain pollution fractions or indicator compounds in urban air. The risks amount to approximately 50 deaths per 100,000 for inhaled particulate organic material (POM), with a contribution from ingested POM about three times larger, and alkenes, and butadiene cause 20 deaths, respectively, per 100,000 individuals. Also, benzene and formaldehyde are expected to be associated with considerable risk increments. Comparative potency methods were applied for POM and alkenes. Due to incompleteness of the list of compounds considered and the uncertainties of the above estimates, the total risk calculation from urban air has not been attempted here.

Cohort study among workers exposed to benzene in China: I. General methods and resources

Benzene is recognized internationally as a leukemogen, but the available data to clarify dose-response relationships and examine risks of malignancies other than leukemia are sparse. A collaborative study was therefore carried out to expand on a previous retrospective cohort mortality study of Chinese benzene-exposed workers. Methods and resources used in the 16-year follow-up of 74,828 benzene-exposed and 35,805 unexposed workers employed for any length of time during 1972-1987 in 712 factories in 12 cities in China are described. Details are provided of the study organization, assessment of benzene exposures since 1949, characterization of factories and workers by exposure status, city, and sex, identification and confirmation of cancers and other deaths, and quality control procedures. The distinguishing features of the study are discussed in relation to earlier cohort studies, and study limitations as well as strengths are presented.

Risk of benzene-induced leukemia: a sensitivity analysis of the pliofilm cohort with additional follow-up and new exposure estimates

This report updates the risk assessment by Crump and Allen (1984) for benzene-induced leukemia that was used by OSHA (1987) to support its reduction of the permissible exposure limit (PEL) to 1 ppm and that also was the basis for EPA's (1985) interim "unit risk" for benzene. The present study derives new risk estimates using data from follow-up through 1987 (whereas the earlier assessment only had follow-up available through 1978), and using new exposure estimates for this cohort developed by Paustenbach et al. (1992) that account for a number of factors that were unknown or not fully evaluated in earlier exposure assessments. There was a significant excess of acute myelocytic or acute monocytic leukemia (AMML, the only forms of acute nonlymphatic leukemia observed) in this cohort, and this end point also exhibited a strong dose-response trend. AMML was the only hematopoietic or lymphatic cancer that was clearly linked to benzene exposure. However, quantitative estimates of risk based on modeling either AMML or all leukemia differed by only 20%. Differences between the two Pliofilm plant locations in the occurrence of AMML were not statistically significant (.12 < or = p < or = .21) after differences in levels of benzene exposure were taken into account. The Paustenbach et al. exposures predicted a quadratic dose response, based on a measure of exposure that weighted intensity of exposure more heavily than duration of exposure. The best-fitting quadratic models predicted an additional lifetime risk of a benzene-related death from 45 yr of exposure to 1 ppm of between 0.020 and 0.036 per thousand. Statistical confidence intervals (90%) on these estimates were barely wide enough to include risk estimates based on linear dose response models. These linear models predicted risks of between 1.6 and 3.1 per thousand.